Freeform fabrication techniques are particularly useful for reducing the design, production and maintenance cycle times associated with the manufacture of three-dimensional objects. In the design phase, freeform fabrication techniques are especially useful for prototyping design concepts, investigating inconsistencies in the design and modifying the design prior to full-scale production. In addition, freeform fabrication techniques have been shown to produce higher quality products at lower cost.
However, the need presently exists for improved freeform fabrication techniques capable of producing complex structures at low cost with minimum set-up and run-time. Many recent techniques, especially in the area of complex metal or ceramic tools, have been developed but remain mostly inadequate. See e.g. J. J. Beaman, N. W. Barlow, D. L. Bourell, R. H. Crawford, H. L. Marcus and K. P. McAlea, "Solid Freeform Fabrication: A New Direction in Manufacturing," ch. 1 (Clair Academic, Boston, Mass. 1997).
The most widely known conventional freeform fabrication system is selective laser sintering ("SLS") as described by D. L. Bourell, H. L. Marcus, N. W. Barlow, J. J. Beaman and C. R. Deckard in U.S. Pat. No. 5,076,869 entitled "Multiple Material Systems for Selective Beam Sintering," which issued in 1991. This method employs a heat laser to fuse or "sinter" selected areas of powdered material such as metal or ceramics. In practice, a vat of powder is scanned by the laser, thereby melting individual particles that in turn stick to adjacent particles. The sintered layer, which is attached to a platform, is lowered into the vat, and new layers are deposited and sintered on top of the previous layers until the entire three-dimensional object or part is produced. An advantage of the sintering method is that the non-heated powder serves as a support for the part as it is formed. Consequently, the non-heated powder can be shaken, dusted or otherwise removed from the resulting object.
Conventional selective laser sintering systems, however, require the use of complex and expensive optical systems where the resolution and level of detail of the final product is limited by the diameter of the laser beam, which is typically 0.25 to 0.50 mm. Furthermore, in an additional step, the powder is deposited and leveled by a rolling brush which requires other electromechanical components. Unfortunately, leveling fine powders with a rolling brush often causes nonhomogeneous packing density. Consequently, an object built from the powder has medium resolution, a non-uniform surface, and often a non-homogeneous structure.
Another conventional method for freeform fabrication involves the use of a three-dimensional ("3-D") printing process to form "green preforms" for powdered ceramic and metal applications. See E. Sachs, M. Cima, P. Williams, P. Brancazio and J. Cornie, "Three-dimensional Printing: Rapid Tooling and Prototypes Directly from a CAD Model," ASME J. Eng. Induct., vol. 114, pp. 481-488 (1992). With this method, a silica binder is printed on selected areas of the powder to form a solid cross-section. The process is repeated to form a tack of cross-sections representing the final object. This approach exhibits the same powder deposition problems as selective laser sintering, along with the additional difficulty of removing unbound powder from internal cavities. Furthermore, objects generated by this system are not recyclable.
In addition, conventional 3-D printing processes are further limited by an inability to automatically remove the media support for over-hangs, large spans, or disjoint areas, and an inability to provide an automated system for physically reproducing three-dimensional computer designs and images. Systems currently available are expensive--the material they use cannot be recycled, and they cannot provide for automated part handling after fabrication due to their use of bulk powders and resins, which require containers rather than conveyor platforms. Accordingly, improvements which overcome any or all of these problems are presently desirable.
Moreover, in addition to the two techniques (SLS and 3-D printing) discussed above, other conventional freeform fabrication schemes include stereo-lithography, shape deposition modeling ("SDM"), fused deposition modeling ("FDM"), and ballistic particle manufacturing ("BPM"). C. W. Hull, U.S. Pat. No. 4,929,402, entitled "Method for Production of Three-Dimensional Objects by Stereolithography" (1991); F. B. Prinz and L. E. Weiss, U.S. Pat. No. 5,207,371, entitled "Method and Apparatus for Fabrication of Three-Dimensional Metal Articles by Weld Deposition," (1993); J. R. Fessler et al., "Laser Deposition of Metals for Shape Deposition Manufacturing," Solid Freeform Fabrication Proceedings, pp. 112-120 (University of Texas, Austin 1996); R. S. Crockett, O. J. Kelly, P. D. Calvet, B. D. Fabes, K. Stuffle, P. Creegan and R. Hoffman, "Predicting and Controlling Resolution and Surface Finish of Ceramic Objects Produced by Stereo deposition Processes," Solid Freeform Fabrication Proceedings, pp. 17-24 (University of Texas, Austin 1995); M. E. Orme and E. P. Muntz, U.S. Pat. No. 5,226,948, entitled "Method and Apparatus for Droplet Stream Manufacturing" (1993). These techniques are based on a raster scanning procedure, which is also know as "point-to-point" fabrication. P. F. Jacobs, "Rapid Prototyping and Manufacturing Fundamental of Stereolithography," pp. 406-411 (Society of Manufacturing Engineering, Dearborn, Mich. 1992) These systems build a single point at a time and consequently only one line or column per scan.
Therefore, a principle object of the present invention is to provide an apparatus and method for manufacturing high quality three-dimensional objects at low cost with minimum setup and run-times.
Another object of the present invention is to provide an apparatus for manufacturing a three-dimensional object utilizing an adjustable planar nozzle for forming a planar jet with uniform thickness.
A further object of the present invention is to provide a high-speed method for manufacturing a three-dimensional object utilizing an adjustable planar nozzle for depositing variable width layers of forming materials.
Yet another object of the present invention is to provide a high-speed method for manufacturing a three-dimensional object utilizing a minimal number of deposition scans per layer of deposited forming materials.
Still another object of the present invention is to provide an apparatus and method for manufacturing a three-dimensional object utilizing a position controllable platform.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying figures showing illustrative embodiments of the invention.